Date

The term of the Basque Parliament expired four years after the date of its previous election, unless it was dissolved earlier. The election decree was required to be issued no later than 25 days before the scheduled expiration date of parliament and published on the following day in the Official Gazette of the Basque Country (BOPV), with election day taking place between 54 and 60 days after the decree's publication.^[3] The previous election was held on 30 November 1986, which meant that the chamber's term would have expired on 30 November 1990. The election decree was required to be published in the BOPV no later than 6 November 1990, setting the latest possible date for election day on 5 January 1991.

The lehendakari had the prerogative to dissolve the Basque Parliament at any given time and call a snap election, provided that no motion of no confidence was in process.^[4] In the event of an investiture process failing to elect a lehendakari within a 60-day period from the Parliament's reconvening, the chamber was to be automatically dissolved and a fresh election called.^[5]

The Basque Parliament was officially dissolved on 3 September 1990 with the publication of the corresponding decree in the BOPV, setting election day for 28 October.^[6]

Electoral system

Voting for the Parliament was based on universal suffrage, comprising all Spanish nationals over 18 years of age, registered in the Basque Country and with full political rights, provided that they had not been deprived of the right to vote by a final sentence, nor were legally incapacitated.^[7]

The Basque Parliament had 75 seats. All were elected in three multi-member constituencies—corresponding to the provinces of Álava, Biscay and Guipúzcoa, each of which was assigned a fixed number of 25 seats to provide for an equal parliamentary representation of the three provinces—using the D'Hondt method and closed-list proportional voting, with a five percent-threshold of valid votes (including blank ballots)^[b] in each constituency.^[8]

The law did not provide for by-elections to fill vacant seats; instead, any vacancies arising after the proclamation of candidates and during the legislative term were filled by the next candidates on the party lists or, when required, by designated substitutes.^[9]

Voting intention estimates

The table below lists weighted voting intention estimates. Refusals are generally excluded from the party vote percentages, while question wording and the treatment of "don't know" responses and those not intending to vote may vary between polling organisations. When available, seat projections determined by the polling organisations are displayed below (or in place of) the percentages in a smaller font; 38 seats were required for an absolute majority in the Basque Parliament.

Polling firm/Commissioner	Fieldwork date	Sample size	Turnout	PNV				EE					Lead
1990 regional election	28 Oct 1990	—N/a	61.0	28.3 22	19.8 16	18.2 13	11.3 9	7.7 6	[c]	0.7 0	8.2 6	1.4 3	8.5
Demoscopia/El País[p 1]	21 Oct 1990	?	?	27.6 21/23	20.8 17/20	17.4 12/14	10.6 7/9	8.2 7	[c]	2.8 0	9.7 6/8	0.3 0	6.8
Opina/La Vanguardia[p 2]	13–16 Oct 1990	2,500	?	28.5 23/25	18.5 15/17	18.0 14/15	11.5 8/9	11.5 8/10	[c]	1.0 0	5.5 3/5	? 0/1	10.0
Metra Seis/El Independiente[p 3][p 4]	14 Oct 1990	?	?	? 22/23	? 15/16	? 12/13	? 10/11	? 8/9	[c]	? 0	6.6 5/6	–	?
Bergareche/Vocento[p 3][p 4]	14 Oct 1990	?	?	? 20/21	? 15	? 13	? 9	? 8/9	[c]	? 0/1	? 8/9	–	?
Sigma Dos/El Mundo[p 3][p 4]	14 Oct 1990	?	?	26.0 19/22	? 17/19	? 13	? 9/10	? 8	[c]	? 0	? 6	–	?
Demoscopia/El País[p 5][p 6][p 7]	27 Sep–3 Oct 1990	1,800	65	26.0 19/21	20.0 18	18.0 13/14	12.0 9/10	10.0 7/9	[c]	? 0	8.0 6/7	–	6.0
Bergareche/Vocento[p 8][p 9]	1 Oct 1990	?	?	? 19/21	? 14/15	? 13	? 9	? 8	[c]	? 0/1	? 8/9	–	?
Basque Government[p 10]	13–16 Dec 1989	?	?	? 20	? 18	? 13	? 8	? 7	[c]	? 0	? 9	–	?
1989 general election	29 Oct 1989	—N/a	66.9	22.8 (17)	21.1 (18)	16.9 (13)	11.2 (9)	8.8 (7)	[c]	3.5 (2)	9.4 (9)	–	1.7
1989 EP election	15 Jun 1989	—N/a	58.5	21.0 (16)	18.2 (17)	19.1 (16)	13.0 (11)	9.8 (8)	[c]	2.7 (1)	7.6 (6)	–	1.9
1987 foral elections	10 Jun 1987	—N/a	67.4	21.8 (16)	18.9 (16)	19.2 (15)	17.6 (15)	9.9 (7)	6.2 (4)	3.4 (2)	–	–	2.6
1987 EP election	10 Jun 1987	—N/a	67.3	19.4 (14)	19.1 (17)	19.6 (16)	16.1 (13)	9.7 (7)	7.2 (6)	3.9 (2)	–	–	0.2
1986 regional election	30 Nov 1986	—N/a	69.6	23.6 17	22.0 19	17.4 13	15.8 13	10.8 9	4.8 2	3.5 2	–	–	1.6

Voting preferences

The table below lists raw, unweighted voting preferences.

Polling firm/Commissioner	Fieldwork date	Sample size	PNV				EE					?	N	Lead
1990 regional election[d]	28 Oct 1990	—N/a	17.2	12.0	11.0	6.9	4.7	[c]	0.4	5.0	0.9	—N/a	38.9	5.2
1989 general election[d]	29 Oct 1989	—N/a	15.1	14.0	11.2	7.4	5.8	[c]	2.3	6.2	–	—N/a	33.0	1.1
1989 EP election[d]	15 Jun 1989	—N/a	12.2	10.6	11.1	7.6	5.7	[c]	1.6	4.4	–	—N/a	41.4	1.1
1987 foral elections	10 Jun 1987	—N/a	14.6	12.6	12.8	11.8	6.6	4.1	2.3	–	–	—N/a	32.6	1.8
1987 EP election[d]	10 Jun 1987	—N/a	12.9	12.7	13.1	10.7	6.5	4.8	2.6	–	–	—N/a	32.6	0.2
1986 regional election[d]	30 Nov 1986	—N/a	16.3	15.2	12.0	10.9	7.5	3.3	2.9	–	–	—N/a	30.4	1.1

Overall

← Summary of the 28 October 1990 Basque Parliament election results →

Parties and alliances		Popular vote			Seats
		Votes	%	±pp	Total	+/−
	Basque Nationalist Party (EAJ/PNV)	289,701	28.28	+4.68	22	+5
	Socialist Party of the Basque Country (PSE–PSOE)	202,736	19.79	−2.16	16	−3
	Popular Unity (HB)	186,410	18.20	+0.80	13	±0
	Basque Solidarity (EA)	115,703	11.30	−4.47	9	−4
	People's Party (PP)1	83,719	8.17	+3.33	6	+4
	Basque Country Left (EE)	79,105	7.72	−3.11	6	−3
	United Left (IU/EB)	14,440	1.41	+0.82	0	±0
	Alavese Unity (UA)	14,351	1.40	New	3	+3
	Democratic and Social Centre (CDS)	6,680	0.65	−2.87	0	−2
	Socialist Democracy (DS)	5,023	0.49	New	0	±0
	The Ecologist Greens (LVE)	4,304	0.42	New	0	±0
	Ruiz-Mateos Group–European Democratic Alliance (ARM–ADE)	4,303	0.42	New	0	±0
	Basque Country Greens (EHB)	4,199	0.41	New	0	±0
	Workers' Socialist Party (PST)	3,010	0.29	+0.04	0	±0
	Humanist Party (PH)	825	0.08	−0.04	0	±0
	Revolutionary Communist League–Communist Movement (LKI–EMK)	670	0.07	New	0	±0
	Alliance for the Republic (AxR)2	669	0.07	−0.03	0	±0
	Communist Party of the Basque Country People (PCPE/EHAC)	599	0.06	New	0	±0
	Communist Party of Spain (Marxist–Leninist) (PCE (m–l))3	272	0.03	−0.07	0	±0
Blank ballots		7,580	0.74	+0.30
Total		1,024,299			75	±0
Valid votes		1,024,299	99.50	+0.09
Invalid votes		5,158	0.50	−0.09
Votes cast / turnout		1,029,457	60.99	−8.63
Abstentions		658,479	39.01	+8.63
Registered voters		1,687,936
Sources[10][11][12]
Footnotes: 1 People's Party results are compared to People's Alliance–Liberal Party totals in the 1986 election. 2 Alliance for the Republic results are compared to Internationalist Socialist Workers' Party totals in the 1986 election. 3 Communist Party of Spain (Marxist–Leninist) results are compared to Republican Popular Unity totals in the 1986 election.

Distribution by constituency

Government formation

Investiture
Ballot →		31 January 1991		1 February 1991
Required majority →		38 out of 75		Simple
	José Antonio Ardanza (PNV) • PNV (22) • EA (9) • EE (6)	37 / 75	N	37 / 75	Y
	Abstentions/Blank ballots • PSE (16) • PP (6) • UA (3)	25 / 75		25 / 75
	Absentees • HB (13)	13 / 75		13 / 75
Sources[10]